RFR: 8316669: ImmutableOopMapSet destructor not called

[Thomas Schatzl]

On Thu, 21 Sep 2023 19:29:19 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/share/code/codeBlob.cpp line 179:
>> 
>>> 177:   if (_oop_maps != nullptr) {
>>> 178:     _oop_maps->~ImmutableOopMapSet();
>>> 179:     FREE_C_HEAP_ARRAY(unsigned char, _oop_maps);
>> 
>> Using FREE_C_HEAP_ARRAY here is concerning (even if it worked for years). CodeBlob should not know what `_oop_maps` is look like inside - he sees its type is `ImmutableOopMapSet*` and not an array.
>> 
>> Thank you for adding the destructor. It should free memory used by `_oop_maps`.
>
> If you are not comfortable to do such changes, file separate RFE to fix it later.

>   Thank you for adding the destructor. It should free memory used by _oop_maps.

I can do that, but that would mean that the object would free its own memory it is running on which seems unusal.

Maybe it is best to add a static free_oop_map_set or similar method to ImmutableOopMapSet that frees that memory? Then that class would nominally both allocate and deallocate that object's memory.

What do you think?

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PR Review Comment: https://git.openjdk.org/jdk/pull/15862#discussion_r1333551639